[Cost-benefit analysis of netting cultivation to block the spread of Oncomelania snails in lake regions].

OBJECTIVE: To evaluate the cost-benefit of netting cultivation to block the spread of Oncomelania snails in lake regions. METHODS: The cost-benefit of netting cultivation was investigated by interviewing in the field, the cost of Oncomelania snail survey and control was investigated by retrospective review in Gaoyou Lake regions of Jinhu County from 2009 to 2011. The benefit of netting cultivation to block the spread of snails in lake regions was calculated by the benefit-cost ratio (BCR), and then the cost-benefit of them was calculated. RESULTS: The area of netting cultivation in Gaoyou Lake regions was 70.77 hm2, the average cost of netting cultivation was 495,595 yuan every year, the average income was 962,000 yuan every year, and the average benefit of netting cultivation was 466 405 yuan. The average cost of Oncomelania snail survey and control from 2009 to 2011 was 85,047.87 yuan in Gaoyou Lake regions. The ratio of cost-benefit was 1.11:1. The benefit was more than the cost. CONCLUSION: There is a well benefit in lake regions during blocking the spread of snails by netting cultivation.

[Evaluation of integrated control measures for soil-transmitted nematodiasis in Jinhu County, Jiangsu Province].

OBJECTIVE: To evaluate the effect of integrated control measures on soil-transmitted nematodiasis so as to provide the evidence for formulating the appropriate control strategies and measures in Jinhu County, Jiangsu Province. METHODS: Since 1995, the comprehensive control measures were carried out for soil-transmitted nematodiasis, and the measures included deworming, health education, safe water, sanitation and environmental remediation. The effects of the comprehensive control measures were evaluated by the investigations of the prevalence of soil-transmitted nematodiasis, awareness of health knowledge, and behaviors of residents. RESULTS: From 1995 to 2012, 646,437 person--times were administrated in deworming medication with 2.48 times per capita; the benefit rate of safe water was 97.90%; the popularity rate of harmless toilets was 86.89%. The awareness rate of health knowledge increased from 54.05% in 1996 to 95.60% in 2012, the difference between them were statistically significant (chi2 = 230.92, P < 0.01); the rate of correct health behaviors increased from 59.07% in 1996 to 96.40% in 2012, the difference between them had statistical significance (chi2 = 202.69, P < 0.01). The prevalence of soil-transmitted nematodiasis decreased from 62.57% in 1989 to 1.21% in 2012, the difference had statistical significance (chi2 = 1016.92, P < 0.01). The infection rates of Ascaris lumbricodes, hookworm and Trichuris trichiura were 0.58%, 1.12% and 0, respectively in 2012, and compared with the rates of those infections in 1989, the decline rates were 94.96%, 97.28% and 100% respectively, the differences between them were statistically significant (chi2 Ascaris = 129.50, chi2 hookworm = 544.62, chi2 Trichurisch = 254.19, all P < 0.01). CONCLUSION: The comprehensive control strategies and measures are effective and soil-transmitted nematodiasis has been controlled in Jinhu County.

[Further study on possibility of diffusion of Oncomelania hupensis with water in river channels of the east route of South-to-North Water Diversion Project].

OBJECTIVE: To study the drifting law of floats and potential risks of Oncomelania hupensis diffusion in the water diversion rivers of the east route of South-to-North Water Diversion Project. METHODS: The O. hupensis snails in the river channels were monitored by the salvage method and snail luring method with rice straw curtains, and the diffusion possibility of snails along with water was assessed through the drift test of floats with GPS. RESULTS: In the flood seasons from 2006 to 2013, totally 8 338.0 kg of floats were salvaged, and 2 100 rice straw curtains were put into water in the Li Canal and Jinbao shipping channel, but no Oncomelania snails were found. The drift test of floats with GPS before water diversion showed that the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.56 - 0.60 m/s, and the average drift distances each time were 999.70 - 1 995.50 m in the Gaoshui River section, while there were no obvious drift in Jinbao shipping channel section. During the water diversion period, the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.35 - 0.41m/s, and the average drift distances each time were 1 248.06 -1 289.44 m in the Gaoshui River, while in Jinbao shipping channel section, the flow velocity on water surface was 0.28 m/s, the average drift velocity of the floats was 0.25 - 0.27 m/s, and the average drift distances each time were 477.76 - 496.38 m. The drift test showed that the floats gradually closed to the river bank as affected by water flow, wind direction and ship waves, when blocked by the reeds, water plants or other obstacles, and they would stopped and could not continue to drift without outside help. CONCLUSIONS: There are no Oncomelania snails found in the river channels of the east route of South-to-North Water Diversion Project. The drifting distance of the floating debris along with the water is restricted by the flow rate and shore environment.

[Study on potential risks of schistosomiasis transmission in Grand Canal West water diversion route of eastern route project of South-to-North Water Diversion Project].

OBJECTIVE: To understand the potential risks of Oncomelania hupensis diffusion and schistosomiasis transmission in the Grand Canal west water diversion route of the eastern route project of the South-to-North Water Diversion Project. METHODS: The engineering layout from Nanyun west floodgate to Hongze Lake, the aquaculture along Hongze Lake, and the data of hydrology and transferred water were investigated. The investigations on Oncomelania hupensis and schistosomiasis were carried out in the surveillance sites of Jinbao Channel and Hongze Lake. The possibilities of snail spreading and schistosomiasis transmission were researched. RESULTS: Oncomelania snails lacked their breeding environment and ecological condition in the Hongze Lake region. The engineering facilities of the Jinhu and Hongze pumping stations went against the snail spreading. The water levels at all steps decreased gradually from Hongze Lake to Jinbao Channel. Therefore, the pumping stations were necessary when the water transferred to Hongze Lake. The multi-year average diverted water volume reached 2.558 billion cubic meters a year in the Jinbao Channel. Of the total diverted water volume, there was 75% of the volume in drought years. The Oncomelania snails were not found in the surveillance sites of the Jinbao Channel and the Hongze Lake region from 2008 to 2011. A total of 3 088 residents were examined with the serology tests and the positive rate was 0.29% in 2008. Totally 4 758 overwater flow people were examined with the serology tests and the positive rate was 2.42% from 2008 to 2011. The serum positive rate was higher in the overwater flow people than that in the residents (chi2 = 0.083, P < 0.01). The stool examinations were all negative in the above mentioned serum positive people. CONCLUSIONS: The Hongze Lake area has still no Oncomelania snail breeding and schistosomiasis endemic so far. There are also no schistosomiasis re-prevalent signs in the Jinbao Channel area where schistosomiasis was once prevalent. The Oncomelania snail breeding and diffusion, and schistosomiasis endemic are unlikely to appear in the Grand Canal west water diversion route of the eastern route project of the South-to-North Water Diversion and Hongze Lake area.

[Study on surveillance and early-warning system of schistosomiasis in first phase of east route of South-to-North Water Diversion Project. III. Indexes of surveillance and early-warning and risk assessment].

OBJECTIVE: To establish the index system of surveillance and early-warning on schistosomiasis and to provide the scientific basis for risk assessment and emergency plan in first phase of east route of South-to-North Water Diversion Project. METHODS: The Delphi method and the multidimensional synthetic evaluation were used in the evaluation of indexes of surveillance and early-warning on schistosomiasis in the east route of the project. RESULTS: There were 53 indexes evaluated in the index system, and among them, there were 3 first grade indexes, 10 second grade indexes and 40 third grade indexes. The indexes on Oncomelania snails were the most important. According to the habitation position of snails, the four grades on surveillance and early-warning of schistosomiasis were established in the east route. The grade I of the early-warning meant that snails crossed the first level of the pumping station. The grade II meant that snails crossed N 32 degrees 54'. The grade III meant that snails crossed N 33 degrees 03' or Jinhu pumping station. The grade IV meant that snails crossed N 33 degrees 15' or Hongze Station. Other 4 indexes on schistosome infection in people and livestock were confirmed as indicative indexes. According to the relationship among the indexes, the evaluation methods were determined on the risk of schistosomiasis transmission. CONCLUSIONS: The index system of surveillance and early-warning and the methods of risk assessment of schistosomiasis have been confirmed in first phase of east route of South-to-North Water Diversion Project. The primary index is related to snails and the supplementary is related to schistosome infection in people and livestock in the system.

[Surveillance of schistosomiasis in Jinbao Channel areas in east route of South-to-North Water Diversion Project].

OBJECTIVE: To understand the dynamic of the endemic situation of schistosomiasis in Jinbao Channel areas, so as to provide the evidence for surveillance and early-warning of schistosomiasis in the east route of the South-to-North Water Diversion Project. METHODS: The conventional methods were used for the surveillance of Oncomelania hupensis snails in the first grade tributary and the flood land of Jinbao Channel. The methods of net salvage and attracting snails with rice straw curtains were used for snail surveys underwater in the surveillance sites. The residents, fishermen and crew were surveyed for schistosomiasis in the regions along the Jinbao Channel. The situation of the fishing boats carrying snails were surveyed, too. RESULTS: The accumulated areas where snails checked were 364.20 hm2. A total of 2 785 kg floats were collected and 400 pieces of rice straw curtains were placed in the surveillance sites, but no snails were found from 2006 to 2010. A total of 7 951 persons were surveyed for schistosomiasis by the serological test, and the total positive rate was 0.92%. The positive rates in the residents and fishermen were 0.79% and 1.55%, respectively. The fishmen's seropositive rate was higher than the residents' (chi2 = 7.11, P < 0.01). A total of 65 people received fecal examinations and there was one infected case. A total of 54 fish boats and 93 fishing gears were detected and no snails were found. CONCLUSIONS: There are no snails and schistosomiasis transmission, but there are the risks of imported schistosomiasis infectious source in the regions along the Jinbao Channel in the east route of the South-to-North Water Diversion Project, therefore, the long-term surveillance is necessary.